NETL researchers devise process to create energy and fuel from slag

19 August 2014

Researchers at the US Department of Energy (DOE) National Energy Technology Laboratory (NETL) have discovered that by mixing two particular types of slag at a unique ratio they can generate energy and fuels (CO and H2). Slag is a molten mixture of process waste ashes from the power and metallurgical industries. In gasification, slag is made from mineral impurities that remain after a carbon feedstock such as coal has been gasified. In metal refining, slag contains impurities removed from a metal while it is refined.

One of the slags in the method is a byproduct of a metallurgical process that is rich in calcium oxide. The other slag contains high levels of vanadium (III) oxide generated during gasification using petroleum coke-based carbon feedstocks.

When the two slags, molten at discharge, are mixed together in the presence of carbon dioxide, the resulting chemical reactions give off an incredible amount of heat—enough to turn a turbine and generate electricity. Simultaneously, the same chemical reactions turn CO2 into carbon monoxide (CO), which can be combusted with oxygen for additional power generation or used as a raw material for producing chemicals such as synthetic petroleum.

More value exists in CO because it allows you to do things that CO2 doesn’t.

—James Bennet

If practiced successfully, the method developed by Jinichiro Nakano and James Bennet could reduce the CO2 emissions from a single steel plant that produces 7,680 tons of steel per day by 0.6 million tons per year without compromising the plant’s rate of production.

Hydrogen gas, which is useful in chemical manufacturing and industrial applications including fuel cells, can be economically made from water using the same method. Nakano and Bennett describe the reactions that yield these products in an article recently published in the International Journal of Hydrogen Energy.